The rotameter operation is based on Variable Area Principle. Fluid flow raises a float in a tapered tube, increasing the area of passage of the fluid. The greater the flow rate, the higher the float is raised. The level of the float is directly proportional to the flow rate. The float reaches the stable position in the tube when the upward force entered by the flowing liquid equals to the downward gravitational force entered by the weight of float. Aster provides a full range of rotameters for your applications.